The United States and Russia have established a communication channel where both sides can notify each other of any potential operation that may be nearby to avoid any possible miscalculations near Ukraine.

The communication line is basically an exchange of phone numbers between the two sides for quick access. The US side will be directed from the US European Command operations center in Stuttgart, Germany, while the Russian side is expected to be coordinated from the Defense Ministry in Moscow, a second senior defense official said.

The United States wanted a channel of communication because American and Russian troops are now operating on the so-called eastern flank near the airspace of Ukraine and Belarus where Russian forces are preparing and attacking.

The second official wasn’t sure what events would specifically trigger a phone call from either side, but the general idea is to ensure that “we can reduce the risk of miscalculation and potential misunderstanding” given the potential proximity of forces. It was also not immediately clear to what extent NATO aircraft would be included in the deal. It is also unclear whether US and Russian ships are included.

Air operations are particularly affected due to the high speed and relatively short distances at which encounters could occur given that Russian aircraft operate close to areas where US troops are located in Poland, Romania and the Baltics. .

The establishment of the agreement is particularly notable because so far Pentagon officials have said they have had no direct communication with their Russian counterparts since the invasion.

There had been an effort to establish the line of communication since late last month. US Defense Secretary Lloyd Austin last spoke with Russian Defense Minister Sergey Shoygu on February 18. The pair also spoke to each other a week earlier. Chairman of the Joint Chiefs of Staff General Mark Milley last spoke with Russian Chief of Staff General Valery Gerasimov on February 11.

The United States specifically rejected a no-fly zone over Ukraine, saying it would put American pilots in a combat scenario to enforce such a plan. But the door is not closed on a potential future air humanitarian corridor to ensure the safe flight of relief supplies, hostilities cease, officials said.

More background: A deconfliction protocol has existed for several years between US and Russian forces in Syria. For the most part, it worked, although US officials repeatedly complained that the Russians did not give enough advance warning of their operations. The United States does not give detailed information to Russia, but informed them recently when American planes would operate in a wide area northeast of Syria.

NBC News first reported the creation of the deconfliction channel.